how to measure the current of a device atached to the arduino?

Im using a transmitter and reciever activated by arduino
i need to measure the current consumtion of them while transmitting/recieving
how can i do that?
thank you

You can place a shunt resistor(low ressistence) in series with your system, or you can use a hall effect sensor warped around the wire that you want to to mesure.

You need to be more specific. what type of transmitter and receiver. There are current sensing sensors on Ebay for a handful of dollars. Search arduino current sensor.

At the sort of values you are probably talking about (mA) any half-decent multimeter will have a suitable current range. However pulse current during transmit mode may be varying faster than the meter can indicate so you're reading may well be a 'mean' value.

But if your transmitter is outputting kW of RF energy then something more substantial will be required.

The question is not providing sufficient detail to get a proper answer.

You can get gizmos like below to get an idea of the power being used by the arduino. I got one to see just how much current was being used by an ethernet shield. The arduino by itself barley registers any current.